1. Field of the Invention:
The present invention relates to an improvement of a slide type exhaust brake system, connected to the middle of an air release pipe, for imparting braking effects to a vehicle by blockading an exhaust passageway for an exhaust gas running through the air release pipe on the occasion of a sharp descent, typically in a large-sized vehicle such as a truck or a bus.
2. Description of the Prior Art:
This type of conventional exhaust brake system is, as illustrated in FIG. 7, arranged such that: a value mechanism unit is composed of a tabular valve member (13) incorporated into a reciprocatory operation passageway provided in an exhaust brake body, and an auxiliary valve member (17) based on a liner (19) buffer-fitted to a block member (15) engaging with the valve member (13) fixed on the side of the tip of a piston rod (16) and to a lower surface of the block member, which liner (19) slides on the continuous surface of the valve member, the valve member (13) having its bottom wall formed with an exhaust pressure adjusting hole (14) passing therethrough. When opening and closing the exhaust passageway, the tip of the piston rod (6) engages with the fitting portion of the valve member in combination with the block member (15) and an intermediate wall provided on the side of the valve member (13) to effect a downward thrust and lifting. The exhaust passageway is thus opened and closed.
Note that the numeral (14') represents a small-diameter exhaust gas escape hole for preventing an excessive load created when closing the passageway.
There arise, however, the following problems inherent in the prior art valve mechanism unit. The processing becomes quite complicated, which leads to an obstacle to the workability, due to factors suchas: the accurate working associated with requirements for obtaining tightfitting with respect to the narrow slide surface; and configurations of the exhaust pressure adjusting hole (14) penetrating a bottom wall and of the escape hole (14') in regards to a size of the valve member (13) accomodated in the limited space. Besides, the strength of the valve mechanism unit is deteriorated. Since the exhaust pressure adjusting hole (14) is not allowed to have a large diameter, there is not yet attained a drop in exhaust pressure of the exhaust pressure adjusting hole opened in advance of opening the exhaust passageway. In general, the braking function tends to be short of smoothness as well as of rapidness. Because of the fitting (18) to the block member (15) and of a structure of allowing for a relatively narrow width of the liner (19), there are easily caused local abrasion on the mutual slide surfaces or a play due to one-sided impingement. Hence, it follows that a life span of the product diminishes, and the valve mechanism unit does not have a long stretch of durability for the reason of highly frequent repetition of opening and closing operations when being used.